The answer if 7 years, if you multiply 2,000 by .02 it equals 40. so you divide 280 by 40 and get 7
<h2>D. If subjects knew they were receiving an active treatment, researchers would not have known if any improvement was due to the new medication or to the expectation of <u>feeling </u>better. If the researchers knew which subjects received which treatments, they might have treated one group of subjects differently from the other group.</h2><h2 />
For your question... the answer would be D
